Tanker aircraft utilize refueling booms to transfer fuel from tanks within the tanker aircraft to aircraft receiving the fuel while in-flight. Conventional refueling booms are pivotally mounted at one end to the tanker aircraft and typically include a telescoping nozzle with a connector at the opposite end of the boom that connects to a corresponding receptacle of the receiving aircraft. Once connected, fuel is transferred from the tanks within the tanker aircraft to the receiving aircraft via the boom.
Refueling booms are designed to rotate upwards to the tail of the tanker aircraft for stowage in a position that does not interfere with rotation of the tanker aircraft during takeoff operations and to minimize drag on the aircraft when not in use. During refueling operations, typical refueling booms are designed to rotate downwards in position for mating with the receiving aircraft and for transferring fuel. To aid in the process of mating the boom nozzle to the receiving aircraft, conventional booms include control surfaces mounted to the boom that can be manipulated by an operator aboard the tanker aircraft to “fly” the boom as necessary to align the nozzle with the receptacle of the receiving aircraft.
Conventional control surfaces for a refueling boom may include a pair of V-shaped surfaces, or ruddervators, that can be moved independently to control the movement of the boom. Alternatively, some refueling booms have control surfaces that include at least one horizontal control surface for controlling the pitch of the boom, and a pair of canted vertical control surfaces attached to opposing ends of the at least one horizontal control surfaces that are used to control the roll and yaw of the boom. These vertical control surfaces extend substantially upwards from the at least one horizontal control surfaces, with a majority of the vertical surfaces above the horizontal surfaces.
This upward configuration of the vertical control surfaces creates several undesirable results. First, when the refueling boom is stowed and the tanker aircraft is operating on the ground with the auxiliary power unit (APU) running, the exhaust of the APU flows over the at least one horizontal control surfaces and between the vertical control surfaces. If a sufficient cross-wind exists, this APU exhaust can be pushed over a vertical control surface, undesirably heating and buffeting the control surface, potentially leading to premature material failure or defects due to material fatigue.
Second, during cruise flight of the tanker aircraft, ambient airflow over the horizontal stabilizers and elevators of the aircraft creates a turbulent flow aft of the elevator root area. When the refueling boom is stowed during cruise flight, the upward extending vertical control surfaces of the conventional refueling boom may be positioned within this turbulent flow field, creating undesirable buffeting that stresses the control surfaces, which creates additional parasite drag and also could contribute to premature failure or defects. Third, the conventional configuration of the vertical control surfaces positions the aerodynamic center of these surfaces above the refueling boom, which imposes a torque moment on the boom beam, requiring structural solutions that increase the weight of the boom.
It is with respect to these considerations and others that the disclosure made herein is presented.